Do I take it that these were not made in very great numbers? or are there many out there to be discovered?

On eBay some FM models (for instance swan, owl) show up all the time. Some models show up seldom or not at all, so it's difficult to answer your question. I come across "Dancing girl" very seldom which could indicate that they were not made in great numbers, but it's difficult to say for certain.

There are six different Dancing girls, in sizes 220mm and 300mm.

Here is one more picture of my Dancing girl, this time together with a girl/lady from Marcolin's "Rock 'n' Roll" series.